In industrial process plants, process control systems such as Distributed Control Systems (DCSs), Safety Instrumented Systems (SISs), and/or Programmable Logic Controllers (PLCs) operate to control one or more industrial processes executing therein to manufacture, refine, transform, generate, or produce physical materials or products such as paper, pharmaceuticals, petroleum products, plastics, packaging, chemicals, etc. from raw materials. Distributed Control Systems typically include one or more process controllers communicatively coupled to one or more field devices via analog, digital or combined analog/digital buses, or via one or more wireless communication links or networks. The field devices, which may be, for example, valves, valve positioners, switches and transmitters (e.g., temperature, pressure, level and flow rate sensors, and the like), are located within the process environment and generally perform physical or process control functions such as opening or closing valves, measuring process and/or environmental parameters such as temperature, flow, or pressure, etc., to control one or more processes executing within the process plant or system to thereby generate the physical materials or products from raw source materials. Smart field devices, such as the field devices conforming to the well-known Fieldbus protocol may also perform control calculations, alarming functions, and other control functions commonly implemented within the controller. The process controllers, which are also typically located within the plant environment, receive signals indicative of process measurements made by the field devices and/or other information pertaining to the field devices (e.g., via buses, wired communication networks, and/or wireless communication networks) and execute a controller application that runs, for example, different control modules which make process control decisions, generate control signals based on the received information and coordinate with the control modules or blocks being performed in the field devices, such as HART®, WirelessHART®, and FOUNDATION® Fieldbus field devices. The control modules in the controller send the control signals over the communication lines or links to the field devices to thereby control the operation of at least a portion of the process plant or system to thereby control at least a portion of one or more industrial processes running or executing within the plant or system. I/O devices, which are also typically located within the plant environment, typically are disposed between a controller and one or more field devices, and enable communications there between, e.g., by converting electrical signals into digital values and vice versa. As utilized herein, field devices, controllers, and I/O devices are generally referred to as “process control devices,” and are generally located, disposed, or installed in a physical field environment of a process plant.
Some industrial process plants include a safety instrumented system (“SIS”), which generally operates to detect significant safety related problems within the process plant and to automatically close or open valves, remove power from devices, switch flows within the plant, etc., when a problem occurs which might result in or lead to a serious hazard in the plant, such as a spill of toxic chemicals, an explosion, etc. These safety instrumented systems typically have one or more separate controllers apart from the standard process control controllers, which referred to herein as safety system logic solvers or safety controllers, which are connected to safety field devices via buses, communication lines, or wireless networks that are separate from those used for process control and installed within the process plant. The logic solvers execute safety instrumented function (SIF) routines that use the safety field devices to detect process conditions associated with significant events, such as the position of certain safety switches or shutdown valves, overflows or underflows in the process, the operation of important power generation or control devices, the operation of fault detection devices, etc., to thereby detect events within the process plant. When an event, which may be a single condition or the simultaneous occurrence of two or more conditions, is detected, the safety controller takes some action to limit the detrimental nature of the event, such as closing valves, turning devices off, removing power from sections of the plant, etc. Generally, these actions include switching safety devices into a tripped or “safe” mode of operation which is designed to prevent a serious or hazardous condition within the process plant.
Some industrial or process plants additionally or alternatively include one or more PLC (Programmable Logic Controller) control systems. Generally speaking, PLCs are high-reliability automation controllers that are suitable for harsh field environments and that are designed to consistently produce output results in response to input conditions within a limited time constraint. Within PLC control systems, PLCs may connect to various sensors, actuators, and/or other field devices as well as, in some implementations, other controllers, from which inputs are received and processed using control logic with which the PLC has been programmed, and to which resulting outputs are transmitted to thereby control at least a portion of an industrial process within a process plant. Typically, PLCs are programmed or configured using ladder-style logic, although some PLCs may be programmed/configured using state logic, function block diagrams, sequence flowcharts, structured text, instruction lists, other types of programming languages, etc.
Thus, various process control systems (such as DCS, SIS, and PLC discussed above, and/or other types of process control systems) operate within an industrial process plant to control one or more industrial processes executing in real-time or run-time therein via various process control devices. As previously discussed, the term “process control devices” generally refers to field devices, I/O devices, and controllers of a DCS; safety field devices, I/O devices, and safety logic solvers or safety controllers of an SIS; and/or programmable logic controllers and field devices PLC-based control systems, any number of which may be included in a process plant operating to manufacture, refine, transform, generate, or produce an industrial product or material.
Information from various process control devices of the process control system(s) of a process plant may be made available over a data highway or communication network to one or more other hardware devices, such as operator workstations, personal computers or other types of computing devices with user interfaces, data historians, report generators, centralized databases, or other centralized administrative computing devices that are typically placed in control rooms or other locations away from the harsher, physical field environment of the plant, e.g., in a back-end environment of the process plant. Each of these hardware devices typically is centralized across the process plant or across a portion of the process plant. These hardware devices run applications that may, for example, enable a control or a safety system operator to perform functions with respect to controlling a process and/or operating the process plant, such as changing settings of the process control routine or a safety routine; modifying the operation of the control modules within the process controllers, the safety system controllers, the field devices, etc. e.g., by changing their respective configurations; viewing the current state of the process; viewing alarms generated by field devices, the process controllers, or the safety system controllers; simulating the operation of the process for the purpose of training personnel or testing the process control software; keeping and updating a configuration database, etc. The data highway utilized by the hardware devices, controllers, and field devices may include a wired communication path, a wireless communication path, or a combination of wired and wireless communication paths.
As is commonly known, process control devices typically are configured off-line using function block diagrams (FBDs) and/or other suitable configuration tools. Such configuration tools allow the definition and/or the configuration of function blocks and/or control modules, where control modules typically comprise a particular arrangement of a particular set of function blocks. Control objects corresponding to the configured function blocks and/or to the configured control modules are downloaded and instantiated into respective process control devices. When the downloaded control objects are instantiated and executed at their host process control devices, the control objects cause their host process control devices to operate in accordance with their respective configurations to control at least a portion of a process within the process plant.
In some arrangements, control objects of an FBD (e.g., which may include one more function blocks, control modules, etc.) may be distributed amongst several process control devices. When the control objects are instantiated at their respective process control devices, said control objects operating in concert across multiple process control devices may cause a particular control logic to execute to control at least a portion of the process. In these distributed configurations, one particular process control device may be responsible for presenting a collective view of the control logic that is distributively operating amongst multiple process control devices, e.g., for the purposes of presentation at a user interface and/or for consumption by another device of the process control system. Such a responsibility or task is generally referred to herein as “shadowing,” and as such the particular device responsible for the collective view of the control logic may be referred to herein as a “shadowing device,” and others of the multiple process control devices that are operating to execute the control logic (which are is represented by and/or referred to by the shadowing device to consumers) may be referred to herein as “shadowed devices.” Generally speaking dynamic data and other information that is generated, received, and/or observed by the shadowed devices is mirrored at the shadowing device so that the mirrored data is made available at the shadowing device to other devices, modules, function blocks, control objects, and/or other consumers of such data that are included in the process control system.
It is noted that a shadowing device need not be a separate and distinct physical device from other devices. In some implementations, for example, the shadowing device may be an isolated software module that is integral to and executing within a shadowed device or within another device, and the isolated software module may act as a bridge between the native (shadowed) control object and the consumers of data observed by the shadowed control object. It is also noted that the collective view presented by the shadowing device to various consumers within the process control system generally includes real-time, dynamic data that is generated, received, and/or otherwise by shadowed devices while the shadowed devices are on-line and operating in real-time or on-line to control at least a portion of one or more processes executing in the process plant. As such, the various consumers of data that is produced or observed by the control logic or portions thereof need not communicate directly with each process control device participating in the execution of the control logic, but instead may simply communicate with the shadowing device to obtain dynamic, real-time data that is generated, received, and/or observed by multiple shadowed devices participating in the control logic. Thus, in effect, the shadowing device provides real-time data transfer from the shadowed devices to the various consumers of the data.
Shadowing devices may shadow any one or more function blocks, one or more control modules, and/or combinations thereof. For example, when a shadowing device hosts (e.g., provides a collective view of) a control module that comprises one or more function blocks executing in one or more other process control devices, the shadowing device is said to be “shadowing the control module” or “shadowing the module.” Shadowing a control module may be performed for the purposes of user interaction and/or data transfer into and out of the control module, for example.
In another example, a shadowing device hosts (e.g., provides a collective view of) a function block, a portion of which is executed by the physical device in which the shadowing device resides, and another portion of which is executed by another process control device. In this example, the shadowing device is said to be “shadowing the function block.” For instance, a Foundation Fieldbus control strategy may be executed by one or more function blocks executing at a process controller and one or more other function blocks executing in various field devices. The process controller may shadow the one or more other function blocks that are executing in the various field devices, e.g., for purposes of user interaction, data transfer into and out of the function blocks, etc.
Example implementations of known techniques for shadowing control modules and function blocks in process control systems and process plants is found in U.S. Pat. No. 6,738,388 and in U.S. Pat. No. 7,519,083, the contents of which are hereby included by reference herein in their entireties.